Apparatus for analyzing electron energy

ABSTRACT

An apparatus for analyzing electron energy comprises a means for producing an axially symmetrical magnetic field, means for disposing a specimen in said magnetic field, an X-ray source for irradiating the specimen to cause emission of electrons and means for analyzing energies of the electrons focused by the magnetic field.

- i States Patent 1 [111 3,822,382 July 2, 1974 APPARATUS FOR ANALYZING ELECTRON 3,582,649 6/1971 Taylor 250/495 AE ENERGY 3,629,579 12/197] Naitou 250/495 B [75] Inventor: Hirotami Koike, Tokyo, Japan OTHER PUBLICATIONS Fahlman et a1: Arkiv For F sik (Sweden), Vol 32, 73 A N h 1) h Y 1 sslgnee 1,3; 2: Kabush'k' Paper 7, pp. 111-129, (1966). [22] Filed: 1971 Primary ExaminerWalter Stolwein [21] Appl' 172,497 Attorney, Agent, or FirmWebb, Burden, Robinson &

. Webb 52 11.s.c1. 250/305, 250/440 51 11m. c1. non 37/26 [57] ABSMCT [5 Field of Search 250/495 AB, 495 A, 49 5 B, An apparatus for analyzmg electron energy (EOIIIPIISBS 1 250/495 Rv41 9 SE, 305 440 a means for producmg an axially symmetrical magnetic field, means for disposing a specimen in the said [56] References Cited magnetic field, an X-ray source for irradiating the specimen to cause emission of electrons and means for UNITED STATES PATENTS analyzing energies of the electrons focused by the 2,418,228 4/l947 Hillier 250/495 AE magnetic field 3,474,245 10/1969 Kimura et al. 250/495 A 3,567,926 3/l971 Siegbahn 250/495 AB 6 Claims, 12 Drawing Figures 2 f ANALYZER 13 r 3 11 v 6 10 j J? 4 f s 1 g 5 Al I in 4 Y J I 7 5 Q & RECORDER %k i a -o.c.

VOLTAGE SUPPLY XRAY SOURCE SHEEI 1 0F 5 ANALYZER RECWDER J2 JJLLM (RECORDER ANA LYZ ER VOLTA G E SUPPLY X-RAY SOURCE an M14 A $822,382

SHEEY 2 BF 5 ELECTRON DETECTOR RECORDER VARIABLE VOLTAGE SOURCE DIFFERENTIATION CIRCUIT X-RAY SOURCE OUTPUT VOLTAG-E 0F JUZ/RCE 17 ammo/V E/VERG-Y SHEET 0F 5 9 5 ULTRA VIOLET SOURCE VARIABLEi 3 s%-.III%% 6 7 I ELECTRON /4 DETECTOR 6 i J; 7 A l M C I27 DIFFERENTIATION cIRcuIT A 6 x-RAY SOURCE WWW 219m agamaaz SHEET w W 5 VARIABLE VOLTAGE SUPPLY I 3 1 47 ELECTRON x/ 4 DETECTOR 4 42 K;\ 6 J5 18 j RECORDER DIFFERENTIATlON 5 cmcurr 9 X-RAY 8 SOURCE ENERGY ANALYZER RECORDER X-RAY SOURCE ENERGY ANALYZER SHEET 5 0F 5 ENERGY ANALYZER SOURCE ANALYZER 7- erwareexr APPARATUS FOR ANALYZING ELECTRON ENERGY SPECIFICATION emitted from the specimen was analyzed. Heretofore,

various types of apparatus have been proposed for the energy analysis of electrons emitted or emanating from a specimen. In these apparatus, however, since the electrons to be analyzed are not strong enough in intensity, the S/N (signal to noise) ratio is insufficient. Accordingly, it is an advantage of the present invention to overcome the above shortcoming.

Briefly, according to this invention there is provided an apparatus which comprises a means for producing a substantially axially symmetrical magnetic field, a specimen being disposed in the said magnetic field, a radiation source for irradiating a radiation onto the said specimen so as to emanate electrons, and a means for analyzing the energy of said electrons focused by the said magnetic field.

The invention will be described with reference to the embodiments illustrated in the accompanying drawings, in which:

FIG. I is a diagrammatic view of an embodiment of the apparatus according to the invention;

FIGS. 2 and 3 show other embodiments of the inventron;

FIG. 4 shows a wave form of an output signal of the detector in the embodiment shown in FIG. 3;

FIG. 5 shows an electron energy distribution curve on the recorder in the embodiment shown in FIG. 3; and,

FIGS. 6, 7, 8, 9, 10, 11 and 12 are diagrams showing other embodiments of the invention.

In the embodiment shown in FIG. 1, numerals I and 2 denote magnetic poles. These magnetic poles are connected by magnetic yoke 3 which is axially symmetrical. Yoke 3 is wound with excitingcoil 4. By exciting the coil, a magnetic field symmetrical with respect to optical axis 5, is produced between magnetic poles l and 2. The abovedescribed magnetic field need not be strictly axially symmetrical in a range that will not harm the focusing effect of electrons. Specimen 6 is disposed on magnetic pole 1. The specimen and yoke 3 are maintained at the same potential (for instance, ground potential). X-ray 7, emanating from X-ray source 8, passes through hole 9 in the magnetic yoke 3 and then irradiates the specimen causing electrons to emanate from the specimen in all directions. Electrons 10 are spirally focused along optical axis 5 by the magnetic field. Therefore, almost all electrons that emanate from the specimen pass through the hole of magnetic pole 2.

Consequently, since the passed electrons are analyzed by energy analyzer 11, the S/N ratio of the analyzer is improved. The output signal of the analyzer is fed into recorder 12.

In the embodiment shown in FIG. 2, the velocities of electrons emanated from the specimen are reduced by the electrical field so that energy is minimized. Such an apparatus as described above can reduce the intensity of the axially symmetrical magnetic field for focusing electrons. In this embodiment, magnetic pole l holding the specimen is insulated from yoke 3 by means of insulating material 13. Magnetic pole 2 is maintained at a negative potential with respect to the specimen by constant DC. voltage source 14. For instance, in the case of an electron energy distribution of 2.3KeV-2.5I(eV, the output voltage of source 14 is set at about 2I(eV. As a result, since the electron energies are reduced to 0.3KeV-0.5KeV, electrons are efficiently focused by the magnetic field and then passed through the hole of magnetic pole 2.

' In addition to the embodiment shown in FIG. 2, the embodiment shown in FIG. 3 is provided with a means for varying the intensity of the above-described electric field. In this construction, electrons l0 emanated from the specimen are separated according to their energies so that detector means 15 can be utilized for merely measuring the intensity of an electron beam in place of energy analyzer 11 as used in the embodiments of FIGS. 1 and 2. Magnetic pole 2, provided with aperture 16, is made of a non-magnetic material for increasing the separability of the electrons. The output voltage of variable DC. voltage source 17 is applied between the aperture and the specimen.

In this embodiment, when an X-ray is irradiated through hole 8 onto the specimen, the electrons emanated from the specimen are focused by the axially symmetrical magnetic field between magnetic pole l and magnetic pole 2 and then arrive at detector means 15. The potential of the specimen is increased in the positive direction with respect to that of the aperture by varying the output voltage of source 17. Further, electrons emanated from the specimen can arrive at the detector only when the energy of the electron is larger than the energy reduced (the potential difierence) between the specimen and the aperture. Consequently, the output signal having a wave form as shown in FIG. 4 is obtained by the detector means. The output signal of the detector means is differentiated by differentiation circuit 18. FIG. 5 shows the wave form of the output signal of circuit 18.

In the embodiment shown in FIG. 6, a vacuum ultraviolet resonance line is irradiated onto a gaseous specimen, which is fed into the focusing magnetic field from vessel 19 via valve 20 and pipe 21. I-Ie gas is introduced into tube 23 from vessel 22 via valve 24, and then ionized by the discharge between electrodes 25a and 25b so that a vacuum ultraviolet resonance line is generated. The gaseous specimen is irradiated by the line passed through pipe 26. The energies of electrons thus emanated from the gaseous specimen are analyzed in the same manner as the embodiment shown in FIG. 1.

In the embodiment shown in FIG. 7, insulating material 27 is provided between specimen 6 and magnetic pole 1 so that a potential difference can be provided between aperture 16 and specimen 6. In the embodiment shown in FIG. 8, insulating material 28 is provided between aperture 16 and magnetic pole 2 so that a potantial difference can be provided between aper ture l6 and specimen 6.

The embodiment shown in FIG. 9 is characterized in that it generates an axially symmetrical magnetic field by a permanent magnet instead of by the exciting coil.

In this embodiment, permanent magnet 29 and magnetic materials 30, 31 and 32 produce an axially symmetrical magnetic field for focusing electrons emanated from therein.

The embodiment shown in FIG. is so constructed that the axially symmetrical magnetic field is produced only by solenoid 33 without the permanent magnet or the magnetic material yoke.

In the embodiment shown in FIG. 11, the axially symmetrical magnetic field is produced by the magnetic lens of a scanning electron microscope or a transmitted electron microscope. In this embodiment, sample 6 is placed in a space other than that between magnetic poles l and 2. Nevertheless, specimen 6 is inside the magnetic field, distribution of which is shown by curve 34.

In the embodiment shown in FIG. 12, the X-ray generator is located in the magnetic field. The X-ray generator is comprised of ring-shaped filament 35 for emitting electrons 36, spherical shellshaped target 37 for generating X-ray 7 by electron irradiation and ringshaped electrode 38 for introducing electrons 36 to the said target 37. It also includes the voltage source 39 for applying each potential to the said filament, the said electrode and the said target respectively.

Having thus described the invention with the detail and particularity as required by the Patent Laws, what is desired protected by Letters Patent is set forth in the following claims.

I. An apparatus for analyzing electron energy comprising a means for producing a substantially axially symmetrical magnetic field, means for positioning a specimen in the magnetic field, an X-ray source for irradiating the specimen to cause emission of electrons, a means for analyzing energies of the electrons focused by the magnetic field, a baffle having an aperture placed between the specimen and means for analyzing energies of the electrons, and a constant DC. voltage source connected with the baffie and said specimen, the potential of the said baffle being maintained at a negative potential with respect to the specimen.

2. An apparatus according to claim 1, wherein an exciting coil produces the substantially axially symmetrical magnetic field.

3. An apparatus according to claim 1, wherein a permanent magnet produces the substantially axially symmetrical magnetic field.

4. An apparatus for analyzing the electron energy comprising a means for producing a substantially axially symmetrical magnetic field, means for positioning a specimen in said magnetic field, an X-ray source for irradiating the specimen to cause emission of electrons, a means for detecting the said electrons focused by the magnetic field, a baffle having an aperture placed between the specimen and said means for detecting the said electrons, and a variable DC. voltage source for varying the negative potential of the baffle with respect to said specimen.

5. An apparatus according to claim 4, wherein an exciting coil produces the substantially axially symmetrical magnetic field.

6. An apparatus according to claim 4, wherein a permanent magnet produces the said substantially axially symmetrical magnetic field.

- UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3, 822, 382 Dated. July 2, 1974 Inventor Q) Hirotami Koike It is certified that error appears in the above-identifier] patent and that said Letters Patent are hereby corrected as shown below:

After the line listing the application serial number insert the following:

- Foreign Application Priority Data August 19, 1970 Japan 45-72621--.

(SEAL) Attest:

MCCOY M. GIBSON JR. Attesting Officer C MARSHALL DANN Commissioner of Patents FORM po'wso uscoMM-oc scam-Pea U.S. GOVERI dMENT IRIN'IING OFFICE: Hi9 0-365-334. 

1. An apparatus for analyzing electron energy comprising a means for producing a substantially axially symmetrical magnetic field, means for positioning a specimen in the magnetic field, an X-ray source for irradiating the specimen to cause emission of electrons, a means for analyzing energies of the electrons focused by the magnetic field, a baffle having an aperture placed between the specimen and means for analyzing energies of the electrons, and a constant D.C. voltage source connected with the baffle and said specimen, the potential of the said baffle being maintained at a negative potential with respect to the specimen.
 2. An apparatus according to claim 1, wherein an exciting coil produces the substantially axially symmetrical magnetic field.
 3. An apparatus according to claim 1, wherein a permanent magnet produces the substantially axially symmetrical magnetic field.
 4. An apparatus for analyzing the electron energy comprising a means for producing a substantially axially symmetrical magnetic field, means for positioning a specimen in said magnetic field, an X-ray source for irradiating the specimen to cause emission of electrons, a means for detecting the said electrons focused by the magnetic field, a baffle having an aperture placed between the specimen and said means for detecting the said electrons, and a variable D.C. voltage source for varying the negative potential of the baffle with respect to said specimen.
 5. An apparatus according to claim 4, wherein an exciting coil produces the substantially axially symmetrical magnetic field.
 6. An apparatus according to claim 4, wherein a permanent magnet produces the said substantially axially symmetrical magnetic field. 